Caving: a 3D cave survey to complement topography

Where LiDAR fits in caving practice

Classic surveying remains the reference: it is proven, repeatable, independent of electronics and standardised among clubs. A phone’s LiDAR is not meant to replace it or to produce a reference survey. It brings something else: the three-dimensional shape of volumes, hard to render on a plan, and a record of the path that works as a thread back.

For a developed cave, a show cave, a network of decorated passages or a quarry-cave, this model helps prepare an outing, explain a volume at a club meeting or document the evolution of a chamber.

Think of it as a three-way complement. Compass and tape give you a rigorous skeleton; the LiDAR mesh gives you the volume around it; photographs and sketches give you the context. Together they make a cave easier to understand for people who were not there, which is often the real purpose of a survey: sharing what the cave looks like.

What Lidark records

You start a survey at the entrance and progress normally. Meanwhile Lidark builds:

• a 3D mesh of walls and walkable floor, local to the device;
• the walked path, with total development and lowest point relative to the entrance;
• an altitude profile, useful to show shafts, steps and slopes;
• landmarks: junction, shaft, danger, point of interest;
• the return distance along the path and the direction of the next stretch.

What works well, and what works less well

The iPhone’s LiDAR reaches a few metres and position tracking is visual. Passages of modest size, with rough walls rich in detail, are ideal. Be wary of large chambers where walls fall outside range, very smooth or glossy surfaces, water, very uniform clay, mist or suspended dust: all can degrade tracking.

An active cave is no place for an unprotected phone. Plan a waterproof case or a suitable housing, and remember that water, mud and knocks have nothing to do with normal iPhone use. Lidark detects poor tracking, vibrates, and records nothing until it is reliable; but it cannot prevent a dropped phone.

Lighting: torch, headlamp and night vision

LiDAR measures without light, but ARKit tracks position with the camera: it needs a minimum of illumination. Lidark switches the torch on automatically in the dark. Your headlamp lights the walls you sweep. As for the screen, night vision mode turns the whole interface, the map and the camera red, in the spirit of cavers’ lamps, so you are not dazzled when you look at the minimap.

From cave to file

Each survey appears as a 2D plan, a profile and, with Lidark Pro, a 3D view with ceilings removed. Export to PLY (binary) or OBJ lets you take the model into CloudCompare, MeshLab or Blender, for instance to overlay your survey on your topography measurements or to produce a render. See also the guide to underground quarries, technically close.

Safety and ethics

Respect access permission, local regulations and the rules of your federation or club. A cave is a fragile environment: do not break formations, leave nothing behind. Do not venture alone and always tell someone your return time.

Lidark is an orientation aid: it replaces neither a guide, nor a rope, nor a prior reconnaissance of the cave. Always keep two light sources independent of the phone. Practical questions in support.

If you cave with a club, tell your team that you are scanning, and agree when the phone comes out: stopping to scan in a narrow passage can block everyone behind you, and a phone is one more object to protect in tight squeezes.